The parallel connected generators still producing a voltage must have their fields over-excited to compensate for the loss of field excitation of the one generator.

The parallel connected generator which has suffered the loss of field excitation must be immediately disconnected from the bus by tripping its circuit breaker.

The parallel connected generator which has suffered the loss of field excitation must have its prime mover immediately stopped.

The parallel connected generator which has suffered the loss of field excitation must have its prime mover immediately reduced to idle speed.